CD8+ and CD4+ T cells are observed in the postmortem human PD brain and MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of PD during its neurodegenerative phase suggesting T cell-mediated dopaminergic toxicity as a putative mechanism (Brochard et al., 2009). This evidence concerns the gene CD4 and Parkinson disease.